Every year downhill skiing causes many serious knee injuries involving ligament and meniscal tears, despite the efforts that have been made in the industry to improve the bindings, and therefore the skier's attachment to the skis.
These injuries often force persons to quit skiing or practicing many other sports. Alternatively, injured persons elect to undergo major surgery that have various risks, are often very painful, involve long recoveries of about six months, and force changes in lifestyle with work, family, professional, psychological and financial drawbacks resulting from the injury.
Other possible injuries while skiing, which follow knee injuries in frequency of occurrence, are head and face injuries, but the use of a helmet to protect against these injuries is becoming increasingly widespread.
Currently, the annual total number of skiers per year between the United States and Europe is about 20 million.
The total number of accidents involving serious injuries entailing caring for and evacuating the injured person from the slope is about between two and four per every thousand. Out of one thousand days skied by a skier, one will be injured between two and four times (in the United States, this figure is about 3.5 per thousand days).
As previously mentioned, skiing involves a high risk of knee ligament and meniscal injuries (between 30% and 40% of the total), among other injuries. Such injuries are frequently caused by the large forces that knees are subjected to because of the stress transmitted to the knee through the rigid boot from the skis, which act as large levers as illustrated in FIG. 1A.
There are different knee injuries, but the most common ones in skiing are external lateral ligament tears (between 20 and 25% of injuries) and the anterior cruciate ligament tears (between 10 and 15% of injuries).
The injury to the external lateral ligament normally affects beginners and intermediate level skiers, who ski mainly in the wedge position, with the feet facing inwards, and who are injured during a fall, when the skis cross over one another or when the wedge opens up. Injury to the external lateral ligament can occur in more experienced skiers when, for example, a ski strikes against an obstacle or when the ski opens up and the skier tries to counter this movement with his leg.
The injury to the anterior cruciate ligament can occur under different conditions, especially in more experienced skiers, and mainly when:                the rear part of the ski acts as a lever with the boot, exerting a torsion force, twisting and bending the knee;        the skier falls backwards during a jump, he or she instinctively straightens his or her leg and therefore falls on the rear part of the ski, forcing the rear part of the boot against the calf, thus diverting the tibia under the femur and tearing the cruciate ligament; or        the skier is upright and is hit from behind on the lower part of the leg, forcing the tibia forwards with the subsequent damage to the cruciate ligament.        
Other injuries include damage to the meniscus (between 5 and 10% of all injuries), caused by torsional stress applied to the flexed knee and usually caused when an obstacle is struck at a high speed.
Currently, bindings holding the boot to the ski are relied upon for reducing the risk of injury, but they do not adequately prevent such risk. Bindings are designed so that the boot is released from the ski when a specific and previously established pressure is surpassed. However, depending on the posture of the leg at the time of the demand of the force and of other factors such as the severity of the impact, it is possible that the binding doesn't behave as expected. In such cases, the binding does not come undone and the boot is not released from the ski at the appropriate time or at all, frequently causing the ligaments of the knee to tear before the mechanism can release the boot.
As previously mentioned, these knee injuries usually bring about an expensive surgical intervention with a long and uncomfortable recovery, results that are not always satisfactory and with significant repercussions in terms of work, family, etc.
Conventional devices do not provide the protection provided by the exoskeleton of the present invention.
For example, U.S. Pat. No. 4,136,404 B1 describes an athletic leg brace apparatus, such apparatus being connected to the sides of a ski boot and including a division of the leg that is hinged at the height of the knee, such that the upper part is attached to the thigh and the lower part to the boot. This apparatus allows flexion and extension movement of the leg, restricting the lateral flexion of the two parts of the leg and allowing the transmission of lateral forces of the skier's legs to the lateral parts of the boot. In other words, the problem to be resolved by this device is the reduction of the lateral flexion of a skier's legs while skiing, and eventually protecting the bones of the leg, not the joints, in the event of flexion but not in the event of torsion, which is the stress causing the most common and significant knee injuries, especially when the knee is extended. Another limitation of the apparatus described in the foregoing US patent is that, since the leg is firmly attached to the boot by this apparatus, when the knee is flexed the freedom of movements is quite compromised, affecting the skiing experience, unlike the device according to the present invention.
U.S. Pat. No. 3,947,051 B1 describes a binding for a ski boot with a transmitter located between the skier's leg and boot to initiate the “release” operation of the binding during falls, particularly forward falls. The transmitter detects an excessive force between the leg and the boot, and transmits an instruction to release the binding, preventing leg injuries in the skier. However, as will be understood, the present invention is completely different from the foregoing patent. For example, according to embodiments of the present invention:                there is not requirement for the replacement of the boot-ski binding mechanism, but rather is complementary to it;        the apparatus is not limited to the boot-ski attachment, but rather may include boot-leg-hip or boot-leg-thigh connecting elements referred to herein as an exoskeleton;        the torque generated in the foot due to the lever effect of the ski in dangerous positions of the knee joint is transmitted to the entire exoskeleton structure and through it to the strong areas of the body, such as to the skier's hip or waist; although it may be transmitted to a part of the skier's leg, such as the thigh;        the device, being attached to strong areas of the body, can withstand the torque generated in the foot due to the lever of the ski in limit to extreme positions that may injure the knee, such that resultant forces are not transmitted to the much weaker knee joint, and which until now no system or mechanism has been able to effectively protect as proven by the previously mentioned injury statistics;        the corporal structure in the areas of the body that are most involved in skiing are significantly reinforced, which allows adjusting the setting of the bindings more tightly with the assurance that no injury will occur; because in most cases the skier would be supported by the reinforced structure of the exoskeleton, and in extreme cases, the binding would come undone without affecting the structure of the knee or any other leg joint or bone.        
None of the previous functionalities are present in U.S. Pat. No. 3,947,051-B1, whereas the present invention allows one to achieve these functionalities.
United States patent application publication number US 2006260620 A1 describes a lower extremity exoskeleton that is linked to a person and configured such that the two leg supports contact the ground to provide support when the user is stopped. The exoskeleton is formed by a link in the thigh, another one in the calf and two joints at the height of the knee, these joints allowing the extension and flexion of the thigh link and of the calf link. The exoskeleton is attached to the hip through joints allowing extension and flexion. The energy for moving the exoskeleton is provided by the user. This device can be used by persons who require aid in walking or who need to be stopped while bearing and carrying loads. That is, the purpose of the device described in United States patent application publication number US-2006260620-A1 is to increase the user's ability to bear large weights when he or she is walking or is stopped.
International patent application number PCT/US2006/014227, describes a variant of the previously described device further incorporating a motor so as to achieve a greater increase in the strength of the person using the exoskeleton.
United States patent application number US 2006260620 A1, which includes an anchoring to the hip, is structured to achieve results that are different from those of the present invention. As previously noted, this application is directed to a system for increasing the ability to bear large loads, to rest while standing or to substitute the lack of strength in weak legs. As such, this system is not useful for practicing a sport that is as dynamic and that requires as much flexibility as, for example, skiing. Rather, it merely has the purpose of increasing the load capacity, whereas, as explained in this specification, the present invention is structured to increase resistance, not strength, against such things as unwanted rotations of a ski.
The system described in United States patent application publication number US 2006260620 A1 is designed to work vertically with movements similar to those carried out while walking, counteracting forces of gravity, but not to resist rotational movements in a horizontal plane, like the invention described herein, which is particularly applicable for snow skiing.
The hip joint described in United States patent application number US 2006260620 A1 does not have a mechanism allowing rotation about all the natural axes and at the same time limiting the potentially injurious angular movement of the knee. On the other hand, the present invention provides a mechanism especially designed to allow all the freedom of movement necessary for such activities as skiing, while preventing unnatural movements that may cause injuries. The present invention is particularly useful for protecting against extreme rotations of the foot, being designed to support rotational forces or torques due to the large lever that is attached to the skier's leg, i.e., the ski, which situation does not occur in the application of the device described in United States patent application publication number US 2006260620 A1.
The knee joint and ankle joint of the device described in United States patent application number US 2006260620 A1 do not have any mechanism allowing the natural movements necessary for activity such as skiing, and which at the same time protects the joint against movements or positions of the knee in particular, and the leg in general, that can cause injuries. On the other hand, the present invention does provide these mechanisms in the joints, on one hand to provide all the necessary range of movements and on the other hand to limit or prevent those movements or positions that may be injurious to the leg in general and the knee in particular, especially focusing on the protection against severe rotations of the foot, or of the body around the foot, which may occur involuntarily during physical activities such as skiing.